Semiconductor fuses are used for various purposes in semiconductor circuits. Such fuses are electrically programmable by the physical alteration of the structure of the fuses. A typical semiconductor fuse structure includes a vertical stack including a silicided semiconducting material, such as polysilicon, and a high-κ/metal gate (HKMG). The stack is patterned such that a narrow, elongated stack is formed to provide a fuse link, which is connected at opposite ends to cathode and anode contacts.
To electrically program the fuse, a programming current is moderated to cause a controlled electromigration of the material inside the electrical fuse structure. This type of programming raises the resistance of the programmed, or blown, fuse compared to that of an intact fuse. By measuring the resistance of an electrical fuse using sensing circuitry, it can be determined whether the electrical fuse has been programmed or is intact. Since the sensing circuitry may interpret any fuse with a resistance less than a lower limit as being intact, it is desirable to ensure that any programmed fuse maintains a resistance above the lower limit to avoid an erroneous reading. An improved electrical fuse structure that produces a high post-programming fuse resistance is therefore desired to reduce the error rate in electrical fuse programming, and thus to increase the reliability of electrical fuse programming.
Degradation of the post programming resistance of such a semiconductor fuse may occur when an HKMG remains underneath the polysilicon of the semiconductor fuse, allowing electrical connection to the anode and cathode contacts to remain, rendering the device insufficient. In gate first technologies, polysilicon fuses are formed concurrently with HKMG transistor gates. Therefore, removal of the HKMG beneath the polysilicon of the fuse would require etching of the polysilicon and HKMG and deposition of a dedicated polysilicon, to build a polysilicon fuse without a HKMG underneath. However, such a process involves an expensive etching step. In addition, amorphous silicon fuses exhibit higher post programming resistance than polysilicon fuses.
A need therefore exists for methodology enabling the cost-effective fabrication of semiconductor fuses for achieving a post-programming resistance distribution with higher resistance values and for enhancing the reliability of electrical fuse programming.